Ghost-free infinite-derivative dilaton gravity in two dimensions

We present the ghost-free infinite-derivative extensions of the Spherically-Reduced Gravity (SRG) and Callan-Giddings-Harvey-Strominger (CGHS) theories in two space-time dimensions. For the case of SRG, we specify the Schwarzschild-type gauge and diagonalise the quadratic action for field perturbations after taking the background fields to be those of the flat-space solution with a linear dilaton. Using the obtained diagonalisation, we construct ghost-free infinite-derivative modifications of the SRG theory. In the context of this modified SRG theory we derive a non-local modification of the linearised spherically-reduced Schwarzschild solution. For the case of CGHS gravity, we work in the conformal gauge and diagonalise the quadratic action associated with this theory for a general background solution. Using these results, we construct the ghost-free infinite-derivative modifications of the CGHS theory and examine non-local modifications to the linearised CGHS black-hole solution.
Comment: 21 pages, 5 figures, version accepted for publication in PRD